A phosphor is a material in which energy of an exciting line is converted to light (an ultraviolet ray, a visible light, or an infrared ray) by exposing the phosphor to a ray such as an ultraviolet ray, a visible light, an infrared ray, a heat ray, an electron beam, an X-ray, or a radiation. The foregoing phosphor-using devices include a fluorescent lamp, an electron tube, a cold cathode display, a fluorescent display tube, a plasma display panel (PDP), an electroluminescence panel, a scintillation detector, an X-ray image intensifier, thermal photoluminescence dosimeter, and an imaging plate (Refer to “Phosphor Handbook” edited by Keikoutai Dougakkai and published by Ohmsha, Ltd.). Those are the devices in which electrical energy is converted to energy of the foregoing exciting line, and this energy is converted further to the foregoing light. Electronic apparatuses which combine such a device with an electronic circuit or a device component such as a light fixture, a computer, a keyboard, or an electronic apparatus without using a phosphor are widely utilized for a display device, lighting equipment and so forth. There are also provided phosphor-using components which combine a phosphor in the form of powder with material except a phosphor such as liquid of water or organic solvent, resin, plastic, and metal or ceramic. Those are widely used, for example, for phosphor coating material in the form of liquid or paste, solids like an ashtray, a direction board, a guide plate, a seal, a stationery product, an outdoor product, and a safety sign plate.
In recent years, PDP has been a focus of constant attention as a flat panel display which can replace a cathode ray tube (CRT) because a large and flat screen is especially possible in PDP. PDP is a display element composed of a number of very small discharge spaces (hereinafter, may be referred to as “display cells”) which are placed in the form of matrix, a discharge electrode is placed within each of display cells, and a phosphor is coated on the inner wall of a display cell. Since an inert gas such as He—Xe, Ne—Xe, or Ar are filled in a space of each of display cells, discharge with the inert gas is generated within each of display cells by applying a voltage to a discharge electrode, and a vacuum ultraviolet ray is radiated. A phosphor is excited by this vacuum ultraviolet ray to emit a visible light. An image is displayed in a display element by luminescence of a phosphor in a display cell at the position where a signal enters. Phosphors, which are used for each of display cells, corresponding to luminescence of blue, green and red respectively are used and a full color can be displayed by being color-coded with those colors in the form of matrix.
Phosphors used mainly for PDP presently are (Y, Gd)BO3: Eu phosphor for a red light emitting phosphor, Zn2SiO4: Mn phosphor for a green light emitting phosphor and BaMgAl10O17:Eu phosphor for a blue light emitting phosphor. It is important that luminescence of the green light emitting phosphor having high visibility especially among those phosphors is intensified in order to enhance white light luminance. In this situation, it is strongly required that luminescence generated by excitation of a vacuum ultraviolet ray of the green light emitting phosphor is further intensified.
It is seen further as a problem that a persistence time is long in Mn-containing phosphors such as Zn2SiO4: Mn and so forth. In such a situation, luminance drops with increase of Mn concentration though it is known that the persistence time becomes short with increase of Mn content. In this manner, luminance and persistence time are presently in a trade-off relation.
Thus, there still remains a critical issue in which the drop in luminance of the foregoing silicate-containing phosphor needs to be suppressed and the persistence time needs to be shortened at the same time.
Usually, a manufacturing method in which a phosphor can be obtained by an inter-solid reaction, using a solid-phase technique after mixing both a given amount of compound containing an activating element and a given amount of compound containing elements comprising a phosphor base and burning them at a given temperature has widely been used as a commonly available manufacturing method of the foregoing phosphor (Refer to “Phosphor Handbook”).
However, it is difficult to manufacture a phosphor having a purely stoichiometric composition by the solid-phase technique and excessive impurities obtained by no reaction or by-product salts produced by reaction may often remain through an inter-solid reaction, so that it becomes difficult to obtain a stoichiometrically high-purity phosphor. As a result, it is pointed out that there appear problems such as a luminance drop of a phosphor and so forth.
On the one hand, it is known that a liquid phase technique is better suited than a solid phase technique for obtaining high-purity phosphor particles having an even composition. It is known that those are oxidized through processes of collection, rinsing, drying and burning by using the following methods such as a reaction crystallization technique, a sol-gel processing, a coprecipitation technique, a hydrothermal synthesis and so forth as commonly available liquid phase techniques for the phosphor manufacturing.
It is also disclosed in Patent Document 1 that there is a method by which a precursor is formed by precipitating salt of organic acid obtained with other elements on the surface of a compound containing a few elements of which a phosphor is composed. But, this method is related to an aluminate phosphor, using an aluminum compound, and information concerning manufacturing of a silicate-containing phosphor for a green light emitting phosphor can not be obtained in Patent Document 1.
Similarly, information concerning manufacturing of a silicate-containing phosphor can not be obtained also in Patent Document 2 and information described in Patent Document 2 is still insufficient from the aspect of reaction since “Reynolds number” is not defined at the time of reaction though a preparation method of a phosphor precursor formed by a reaction tube is disclosed in Patent Document 2. Further, a problem concerning wear performance inside the reaction tube is not also taken into consideration.    (Patent Document 1) Japanese Patent O.P.I. Publication No. 2001-172621    (Patent Document 2) Japanese Patent O.P.I. Publication No. 2003-138253